Functions and performance, which are requested for mobile terminal devices, are being upgraded from year to year. Mobile terminal devices, which are called smart phones that are provided with a larger liquid crystal display screen or touch panel than conventional mobile terminal devices and various devices such as a camera and a global positioning system (GPS), are starting to be widely used. Such mobile terminal devices have preinstalled applications for phone calls, mails, web browsing and the like. Users can install various applications in the mobile terminal devices. Multiple applications can be simultaneously executed in each of the mobile terminal devices. The multifunctional mobile terminal devices tend to consume more power than the conventional mobile terminal devices. Power that can be supplied from batteries included in the mobile terminal devices, however, is limited. Thus, there is a demand to reduce power to be consumed in order to drive the mobile terminal devices with the batteries for a long time.
In order to achieve such performance and satisfy the demand to reduce power to be consumed, mobile terminal devices that each include a multi-core central processing unit (CPU) are starting to be widely used. The multi-core CPU can operate in a plurality of frequency-voltage combinations. The multi-core CPU controls its operating speed and power (to be consumed) by dynamically switching between the frequency-voltage combinations. Each of cores of the multi-core CPU can be set to operate or not to operate so that the number of operating cores is increased or reduced. Thus, the whole throughput of the multi-core CPU and power to be consumed by the multi-core CPU can be adjusted. Various applications are executed in the mobile terminal device. The state of the multi-core CPU is dynamically controlled on the basis of the characteristic and usage status of the multi-core CPU. Thus, operation performance of the multi-core CPU is ensured for a user, and power to be consumed by the multi-core CPU is reduced.
Japanese Laid-open Patent Publication Nos. 2007-334782 and 2008-129846 are examples of related art.